The present disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a perforating gun with a variable free gun volume.
It is well known that a pressure reduction can be experienced in a wellbore when well fluid rushes into void spaces of a perforating gun after the perforating gun is fired. Unfortunately, however, this pressure reduction can be too large, creating an excessively underbalanced condition which can break down a perforated formation near the wellbore, leading to production of sand, etc.
For this reason and others, it would be advantageous to be able to selectively vary a free gun volume of a perforating gun.